14 The American. O r-olog Lit . januarv, uai 
"irnpiilsf" wliifh ;rivos tlio glacier its first inovciiu'iit, (p. 'i). The 
statement foncerniiifjj the orifj^in of tcniiiii.il moraines recognizes only 
superficial material as enterinjf into their constitution, (p. H). Kettle- 
lioles are ascribed to the melting of ice buried l)y debris, (]). 7), but on 
page GS it is only a '"majority" of "kettles." which are thus explained. 
"With the exception of that concerning neve, these definitions are not 
wrong, but they are inc()ni|)lcte. and arc likrly to give use to crronc"- 
ous concept ions. 
The chapter on existing glaciers is a ctin\ ciiient suminarv of known 
data concerning tiie distribution of existing glaciers. It cdultl have 
beendi'sircd that fuller references to authorities had been given here 
.and elsewhere. Perhajjs the ])oi>ular <'haracter of the book makes 
tlieir omission ])ardonable. 
The discussion of the signs of ])ast ghiciation is concise and to the 
])oint and will commend itself to all readers, lint we notice that in 
this connection one line of evidence which is locallycrucial. and al- 
ways significant, viz.: to|)ogra])h_v . is entirely omitted. 
Chapters V, \1 and \l\ are those which will most interest geolo- 
gists. The chapter on ancient glaciers in the western Jiemisphere 
gives a brief account of the glacial period in North Ami'rica. accom- 
panied by much fuller consideration of details concerning tlu' drift 
fornnitions of Pennsylvania than is demanded by the ])ur])oseof the 
book. The details add nothingto the ])ortrayal of the subject in hand^ 
and can iiardly fail to l)e confusing to those who are not geologists. 
The position of the terminal moraine fi-om the At lant ic coast west- 
ward to Ohio is carefully defined. J'>ut where the moraine dej)arts 
from the margin of recognized drift, our autJior lea\es the morainic 
line and traces out the line which nnirks the border of drift, without 
clearly indicating tliat the one line is not a continuation of the other. 
The departure of these two lines from each other west of I'ennsyl- 
vania. taken together with all concomitant ])henomena, is most signi- 
ficant for the theme of the book. To the divergence of these two- 
lines we attach nuicli more importance than does I'rof. Wright. We 
should, tiierefore, have emphasized their separation much more than 
he does. 
Borne ideas advanced in this chai)ter are not likely to cfunmand 
general assent, ('oncerning drumlins in general it is said (p. 7<i) that 
"if time enough had ela])sed, the whole accumulation (of the drum- 
lins) would have been leveled by the glacier, and spread ovit the 
broader area where the more rapid lines of movi'ment became con- 
fluent, and where the differential n)ovement was less marked." Tliis- 
statement would seem to make drumlins the result of a destructive 
process, interrupted before itscomi)letioM. Thisstateinent is made in 
connectioTi with a reference of approval to I'rof. Davis' view concern- 
ing the origin of drumlins, though it is not clear whetiier or not pro- 
fessor Wright means to attribute this particular notion to Davis*. 
The idea that drumlins are the result of a destructive process inter- 
rupted before its completion, finds further expressi<-)n where the 
